U.S. patent number 11,380,864 [Application Number 16/785,300] was granted by the patent office on 2022-07-05 for electronic device, display apparatus, photoelectric conversion apparatus, electronic apparatus, illumination apparatus, and moving object.
This patent grant is currently assigned to Canon Kabushiki Kaisha. The grantee listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Koji Ishizuya, Norifumi Kajimoto, Hiroyuki Mochizuki, Hiroaki Sano, Tetsuo Takahashi.
United States Patent |
11,380,864 |
Takahashi , et al. |
July 5, 2022 |
Electronic device, display apparatus, photoelectric conversion
apparatus, electronic apparatus, illumination apparatus, and moving
object
Abstract
The present disclosure provides an electronic device including a
plurality of first electrodes, a second electrode, a functional
layer disposed between each first electrode and the second
electrode, and an insulating layer having a slope portion on the
first electrode, wherein the functional layer is continuously
disposed so as to cover the first electrode, a neighboring first
electrode, and the insulating layer covering the first electrode
and the neighboring first electrode, the functional layer on the
first electrode has a layer thickness smaller than a height from an
upper surface of the first electrode to an upper surface of the
insulating layer, and the functional layer on the slope portion of
the insulating layer has a layer thickness of 20 nm or more in a
direction perpendicular to a slope surface of the slope
portion.
Inventors: |
Takahashi; Tetsuo (Kawasaki,
JP), Kajimoto; Norifumi (Zama, JP),
Ishizuya; Koji (Fujisawa, JP), Sano; Hiroaki
(Chofu, JP), Mochizuki; Hiroyuki (Atsugi,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
|
Family
ID: |
1000006414687 |
Appl.
No.: |
16/785,300 |
Filed: |
February 7, 2020 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20200259113 A1 |
Aug 13, 2020 |
|
Foreign Application Priority Data
|
|
|
|
|
Feb 13, 2019 [JP] |
|
|
JP2019-023783 |
Nov 20, 2019 [JP] |
|
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JP2019-210033 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
51/56 (20130101); H01L 51/5072 (20130101); H01L
27/3234 (20130101); H01L 51/5056 (20130101); H01L
51/5237 (20130101) |
Current International
Class: |
H01L
51/52 (20060101); H01L 51/50 (20060101); H01L
27/32 (20060101); H01L 51/56 (20060101) |
Field of
Search: |
;257/40 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Tran; Dzung
Attorney, Agent or Firm: Canon U.S.A., Inc. I.P.
Division
Claims
What is claimed is:
1. An electronic device comprising: a first lower electrode; a
second lower electrode; an upper electrode; a functional layer
disposed between each lower electrode and the upper electrode, and
covering each lower electrode; and an insulating layer covering an
edge of each lower electrode, and including a slope portion on each
lower electrode, wherein each lower electrode includes a first
region including the edge of the lower electrode and covered with
the insulating layer, and a second region in contact with the
functional layer, the functional layer is continuously disposed so
as to cover the second region of the first lower electrode, the
second region of the second lower electrode, and the insulating
layer covering the first lower electrode and the second lower
electrode, the functional layer has, on the second region, a layer
thickness smaller than a height from an upper surface of the first
lower electrode to an upper surface of the insulating layer, and
the functional layer on the slope portion of the insulating layer
has a layer thickness of 33 nm or more in a direction perpendicular
to a slope surface of the slope portion.
2. The electronic device according to claim 1, wherein a ratio of a
distance between the second region of the first lower electrode and
the second region of the second lower electrode to the layer
thickness of the functional layer on the second region is less than
50.
3. The electronic device according to claim 1, wherein, in a
section perpendicular to a main surface of the first lower
electrode, the slope portion includes a gentle slope portion
between an upper end of the slope portion and a lower end of the
slope portion, and a steep slope portion disposed between the
gentle slope portion and the lower end and having, relative to the
first lower electrode, a larger slope angle than the gentle slope
portion.
4. The electronic device according to claim 3, wherein the
functional layer includes a charge transport layer in contact with
the first lower electrode, a height of an upper surface of the
charge transport layer on the second region of the first lower
electrode is smaller than a height of an upper end of the steep
slope portion, and a height of an upper surface of the functional
layer on the second region of the first lower electrode is larger
than the height of the upper end of the steep slope portion.
5. The electronic device according to claim 1, further comprising a
substrate on which each lower electrode is disposed, wherein, in
plan view in a direction perpendicular to a main surface of the
substrate, the slope portion and the first region of the first
lower electrode overlap.
6. The electronic device according to claim 1, further comprising a
substrate on which each lower electrode is disposed, wherein the
insulating layer is covered with the functional layer and includes
another slope portion disposed, in plan view in a direction
perpendicular to a main surface of the substrate, between the first
lower electrode and the second lower electrode, and the functional
layer on the other slope portion has a layer thickness of, in a
direction perpendicular to the other slope portion, 20 nm or
more.
7. The electronic device according to claim 1, the electronic
device comprising a plurality of insulating layers including the
insulating layer, which covers an edge of each lower electrode,
wherein each of the plurality of insulating layers includes a slope
portion on each lower electrode, and the functional layer has a
thickness of 20 nm or more in a direction perpendicular to the
slope portion.
8. The electronic device according to claim 7, further comprising a
substrate on which each lower electrode is disposed, wherein the
plurality of insulating layers each include another slope portion
disposed, in plan view in a direction perpendicular to a main
surface of the substrate, between the first lower electrode and the
second lower electrode, and, on the other slope portion, the
functional layer has a thickness of 20 nm or more in a direction
perpendicular to a slope surface of the other slope portion.
9. The electronic device according to claim 1, wherein the slope
surface of the slope portion is not parallel to an upper surface of
the first lower electrode, and the slope surface of the slope
portion is a portion of a surface of the insulating layer, the
portion being disposed between an upper surface of the insulating
layer and an upper surface of the first lower electrode covered
with the insulating layer.
10. The electronic device according to claim 3, wherein the steep
slope portion has a slope angle of more than 50.degree. relative to
the first lower electrode, and the gentle slope portion has a slope
angle of 50.degree. or less relative to the first lower
electrode.
11. The electronic device according to claim 3, wherein the
insulating layer includes the steep slope portion including a
portion having a slope angle of more than 90.degree. relative to
the first lower electrode.
12. The electronic device according to claim 1, wherein the
functional layer is an organic layer including a light emitting
layer.
13. The electronic device according to claim 12, wherein the
functional layer includes a charge transport layer in contact with
the first lower electrode, the charge transport layer is a hole
transport layer, and the light emitting layer is of an electron
trap type.
14. A display apparatus comprising a plurality of pixels, wherein
at least one of the plurality of pixels includes an electronic
device, and a transistor connected to the electronic device,
wherein the electronic device includes a first lower electrode, a
second lower electrode, an upper electrode, a functional layer
disposed between each lower electrode and the upper electrode, and
covering each lower electrode, and an insulating layer covering an
edge of each lower electrode, and including a slope portion on each
lower electrode, wherein each lower electrode includes a first
region including the edge of the lower electrode and covered with
the insulating layer, and a second region in contact with the
functional layer, the functional layer is continuously disposed so
as to cover the second region of the first lower electrode, the
second region of the second lower electrode, and the insulating
layer covering the first lower electrode and the second lower
electrode, the functional layer has, on the second region, a layer
thickness smaller than a height from an upper surface of the first
lower electrode to an upper surface of the insulating layer, and
the functional layer on the slope portion of the insulating layer
has a layer thickness of 33 nm or more in a direction perpendicular
to a slope surface of the slope portion.
15. A photoelectric conversion apparatus comprising: an optical
unit including a plurality of lenses; an image pickup device
configured to receive light having passed through the optical unit;
and a display unit configured to display an image captured with the
image pickup device, wherein the display unit includes an
electronic device including a first lower electrode, a second lower
electrode, an upper electrode, a functional layer disposed between
each lower electrode and the upper electrode, and covering each
lower electrode, and an insulating layer covering an edge of each
lower electrode, and including a slope portion on each lower
electrode, wherein each lower electrode includes a first region
including the edge of the lower electrode and covered with the
insulating layer, and a second region in contact with the
functional layer, the functional layer is continuously disposed so
as to cover the second region of the first lower electrode, the
second region of the second lower electrode, and the insulating
layer covering the first lower electrode and the second lower
electrode, the functional layer has, on the second region, a layer
thickness smaller than a height from an upper surface of the first
lower electrode to an upper surface of the insulating layer, and
the functional layer on the slope portion of the insulating layer
has a layer thickness of 33 nm or more in a direction perpendicular
to a slope surface of the slope portion.
16. An electronic apparatus comprising: a display unit including an
electronic device; a housing provided with the display unit; and a
communication unit provided in the housing and configured to
communicate with an external device, wherein the electronic device
includes a first lower electrode, a second lower electrode, an
upper electrode, a functional layer disposed between each lower
electrode and the upper electrode, and covering each lower
electrode, and an insulating layer covering an edge of each lower
electrode, and including a slope portion on each lower electrode,
wherein each lower electrode includes a first region including the
edge of the lower electrode and covered with the insulating layer,
and a second region in contact with the functional layer, the
functional layer is continuously disposed so as to cover the second
region of the first lower electrode, the second region of the
second lower electrode, and the insulating layer covering the first
lower electrode and the second lower electrode, the functional
layer has, on the second region, a layer thickness smaller than a
height from an upper surface of the first lower electrode to an
upper surface of the insulating layer, and the functional layer on
the slope portion of the insulating layer has a layer thickness of
33 nm or more in a direction perpendicular to a slope surface of
the slope portion.
17. An illumination apparatus comprising: a light source including
an electronic device, and a light diffusion unit or optical film
configured to transmit light emitted from the light source, wherein
the electronic device includes a first lower electrode, a second
lower electrode, an upper electrode, a functional layer disposed
between each lower electrode and the upper electrode, and covering
each lower electrode, and an insulating layer covering an edge of
each lower electrode, and including a slope portion on each lower
electrode, wherein each lower electrode includes a first region
including the edge of the lower electrode and covered with the
insulating layer, and a second region in contact with the
functional layer, the functional layer is continuously disposed so
as to cover the second region of the first lower electrode, the
second region of the second lower electrode, and the insulating
layer covering the first lower electrode and the second lower
electrode, the functional layer has, on the second region, a layer
thickness smaller than a height from an upper surface of the first
lower electrode to an upper surface of the insulating layer, and
the functional layer on the slope portion of the insulating layer
has a layer thickness of 33 nm or more in a direction perpendicular
to a slope surface of the slope portion.
18. A moving object comprising: an illumination unit including an
electronic device; and a body provided with the illumination unit,
wherein the electronic device includes a first lower electrode, a
second lower electrode, an upper electrode, a functional layer
disposed between each lower electrode and the upper electrode, and
covering each lower electrode, and an insulating layer covering an
edge of each lower electrode, and including a slope portion on each
lower electrode, wherein each lower electrode includes a first
region including the edge of the lower electrode and covered with
the insulating layer, and a second region in contact with the
functional layer, the functional layer is continuously disposed so
as to cover the second region of the first lower electrode, the
second region of the second lower electrode, and the insulating
layer covering the first lower electrode and the second lower
electrode, the functional layer has, on the second region, a layer
thickness smaller than a height from an upper surface of the first
lower electrode to an upper surface of the insulating layer, and
the functional layer on the slope portion of the insulating layer
has a layer thickness of 33 nm or more in a direction perpendicular
to a slope surface of the slope portion.
19. The electronic device according to claim 1, wherein a thickness
of the functional layer at the second region is 100 nm or less.
Description
BACKGROUND OF THE DISCLOSURE
Field of the Disclosure
The present disclosure relates to an electronic device, a display
apparatus, a photoelectric conversion apparatus, an electronic
apparatus, an illumination apparatus, and a moving object.
Description of the Related Art
As electronic devices including an organic layer, organic light
emitting elements and organic photoelectric conversion elements
have been proposed. Organic light emitting elements are elements
that include an upper electrode, a lower electrode, and an organic
layer disposed therebetween, and are configured to excite an
organic compound included in the organic layer to thereby emit
light. In recent years, electronic devices including an organic
light emitting element have been attracting attention. In
particular, display apparatuses are widely used.
There are known modes of forming organic layers of organic light
emitting elements: a mode of forming organic layers having
different configurations for individual emission colors, and a mode
of forming organic layers having the same configuration for
different emission colors. In the mode of forming organic layers
having the same configuration for different emission colors, an
organic layer is typically formed so as to continuously extend for
a plurality of light emitting elements. Even in the case of forming
organic layers having different configurations for individual
emission colors, some of the organic layers may be formed so as to
continuously extend for a plurality of light emitting elements.
However, in such a structure in which organic layers continuously
extend for a plurality of light emitting elements and between a
plurality of light emitting elements, current tends to leak via
organic layers between adjacent light emitting elements. The
leakage current between light emitting elements causes
unintentional emission from light emitting elements. The
unintentional emission from light emitting elements narrows color
gamut, which indicates the display performance of the display
apparatus.
In a photoelectric conversion element including an organic layer,
an organic photoelectric conversion layer is disposed so as to
continuously extend to cover a plurality of lower electrodes. In
this case, leakage current flows via the organic photoelectric
conversion layer between the plurality of lower electrodes, which
may result in generation of noise.
When such an organic layer is formed as a thin layer, leakage
current between the lower electrodes can be reduced. However, when
the organic layer is thin, leakage current tends to flow between an
upper electrode and a lower electrode. Japanese Patent Laid-Open
No. 2007-73608 discloses, in order to reduce short circuits between
an upper electrode and a lower electrode, a display apparatus in
which an organic layer has, in a pixel peripheral area near the rib
for dividing pixels, a larger layer thickness than in a pixel
central area.
Further, Japanese Patent Laid-Open No. 2007-73608 describes the
relation between the layer thickness of the organic layer in the
pixel central area and the layer thickness of the organic layer in
the pixel peripheral area, but does not describe, on a slope
portion of the rib for dividing pixels, the layer thickness of the
organic layer measured in a direction perpendicular to the slope
portion. The control of the ratio of the thickness of the organic
layer in the pixel central area to the thickness of the organic
layer in the pixel peripheral area alone is insufficient for a
reduction in the leakage current between the upper electrode and
the lower electrode due to, on the slope portion of the rib for
dividing pixels, the layer thickness of the organic layer measured
in a direction perpendicular to the slope portion.
SUMMARY OF THE DISCLOSURE
The present disclosure provides an electronic device including a
plurality of first electrodes in which leakage current between the
plurality of first electrodes is reduced, and leakage current
between such a first electrode and a second electrode is
reduced.
An electronic device according to an embodiment of the present
disclosure includes a first lower electrode; a second lower
electrode; an upper electrode; a functional layer disposed between
each lower electrode and the upper electrode, and covering each
lower electrode; and an insulating layer covering an edge of each
lower electrode, and including a slope portion on each lower
electrode, wherein each lower electrode includes a first region
including the edge of the lower electrode and covered with the
insulating layer, and a second region in contact with the
functional layer, the functional layer is continuously disposed so
as to cover the second region of the first lower electrode, the
second region of the second lower electrode, and the insulating
layer covering the first lower electrode and the second lower
electrode, the functional layer has, on the second region, a layer
thickness smaller than a height from an upper surface of the first
lower electrode to an upper surface of the insulating layer, and
the functional layer on the slope portion of the insulating layer
has a layer thickness of 20 nm or more in a direction perpendicular
to a slope surface of the slope portion.
Further features of the present disclosure will become apparent
from the following description of example embodiments with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic sectional view of the configuration of an
organic device according to a first example embodiment of the
present disclosure.
FIG. 2 is a schematic plan view of an example configuration of the
organic device in FIG. 1.
FIG. 3 is a schematic view and circuit diagram of an example
organic light emitting device according to an embodiment.
FIG. 4 is a graph of the chromaticity of a red pixel to a ratio of
the distance between openings of two adjacent first electrodes to
the layer thickness of the organic layer on the first
electrodes.
FIG. 5A is an enlarged view of the schematic sectional view
illustrating the configuration of the organic light emitting device
according to the first embodiment of the present disclosure. FIG.
5B is an enlarged view of a schematic sectional view illustrating
the configuration of an organic light emitting device of a
comparative example.
FIG. 6 is an enlarged view of a schematic sectional view
illustrating the configuration of an organic light emitting device
according to a second embodiment of the present disclosure.
FIG. 7 illustrates members disposed in vapor deposition
simulation.
FIG. 8 is a graph of the results of the vapor deposition
simulation.
FIG. 9 is a schematic view of an example of a display apparatus
according to an embodiment.
FIG. 10A is a schematic view of an example of an image pickup
apparatus according to an embodiment. FIG. 10B is a schematic view
of an example of an electronic apparatus according to an
embodiment.
FIG. 11A is a schematic view of an example of a display apparatus
according to an embodiment. FIG. 11B is a schematic view of an
example of a foldable display apparatus.
FIG. 12A is a schematic view of an example of an illumination
apparatus according to an embodiment. FIG. 12B is a schematic view
of an example of an automobile including a vehicle illumination
unit according to an embodiment.
FIG. 13 is a graph of leakage current between an upper electrode
and a lower electrode against the layer thickness of the thinnest
portion of an organic layer on a slope portion measured in a
direction perpendicular to the slope portion.
DESCRIPTION OF THE EMBODIMENTS
An electronic device according to an embodiment of the present
disclosure includes a first lower electrode; a second lower
electrode; an upper electrode; a functional layer disposed between
each lower electrode and the upper electrode, and covering each
lower electrode; and an insulating layer covering an edge of each
lower electrode, and including a slope portion on each lower
electrode, wherein each lower electrode includes a first region
including the edge of the lower electrode and covered with the
insulating layer, and a second region in contact with the
functional layer, the functional layer is continuously disposed so
as to cover the second region of the first lower electrode, the
second region of the second lower electrode, and the insulating
layer covering the first lower electrode and the second lower
electrode, the functional layer has, on the second region, a layer
thickness smaller than a height from an upper surface of the first
lower electrode to an upper surface of the insulating layer, and
the functional layer on the slope portion of the insulating layer
has a layer thickness of 20 nm or more in a direction perpendicular
to a slope surface of the slope portion.
An electronic device according to an embodiment of the present
disclosure includes an element including a first electrode, a
second electrode, a functional layer disposed between the first
electrode and the second electrode, and an insulating layer
covering an edge of the first electrode.
As described above, in the electronic device including a plurality
of first electrodes in which leakage current between the first
electrodes is reduced, the functional layer on the slope portion of
the insulating layer has a layer thickness of 20 nm or more, to
thereby reduce leakage current between such a first electrode and
the second electrode.
This effect of reducing leakage current provided by setting the
thickness of the functional layer as described above is strong in
the case where the functional layer has a layer thickness smaller
than the height of insulating layers covering edges of the
plurality of first electrodes, in other words, in the case where
the functional layer is thin. The effect is also strong in the case
where the functional layer is continuously formed for a plurality
of elements, in other words, in the case where the functional layer
is formed as a continuous layer.
When the electronic device includes an organic light emitting
element, by forming the functional layer, namely, the organic
layer, so as to have a small layer thickness, light emission
efficiency can be improved. This is achieved by a reduction in the
amount of light absorbed by the organic layer. A distance L between
a pair of electrodes of the organic light emitting element can
satisfy Formula (1) below. When the organic light emitting element
satisfies Formula (1) below, constructive optical interference
between electrodes is caused, which results in a further increase
in the light emission efficiency of the organic light emitting
element. The light emission efficiency here can also be referred to
as extraction efficiency.
(.lamda./8).times.(-(2.PHI./.pi.)-1)<L<(.lamda./8).times.(-(2.PHI./-
.pi.)+1) (1)
In Formula (1), .lamda. represents the wavelength of a maximum peak
in an emission spectrum of light emitted from the light emitting
layer included in the organic layer. The maximum peak is, among
peaks in the emission spectrum, a peak having the highest
intensity. The wavelength of this peak may be the shortest
wavelength among peaks included in the emitted light. .PHI.
represents a phase shift at an electrode. The phase shift occurs
upon reflection of light. One of the first electrode and the second
electrode may be a reflective electrode, and the other may be a
light transmission electrode. The light transmission electrode may
be an electrode that transmits a portion of light and reflects the
other portion of light.
An element of an electronic device according to an embodiment of
the present disclosure may be an organic light emitting element.
When the element is an organic light emitting element, the
functional layer may be an organic layer including a light emitting
layer. Alternatively, the element may be a photoelectric conversion
element. When the element is a photoelectric conversion element,
the functional layer may be an organic layer including a
photoelectric conversion layer.
The first electrode includes a first region covered with an
insulating layer and including an edge of the first region, and a
second region not covered with the insulating layer and being in
contact with the functional layer. The first region may surround
the second region.
In an organic light emitting device according to an embodiment of
the present disclosure, an organic layer 4 can have, on the second
region of each first electrode, a layer thickness of less than 100
nm. This tends to provide higher luminance, and provides a stronger
effect of reducing leakage current between the first electrode and
the second electrode due to the present disclosure.
Hereinafter, specific examples of an electronic device according to
an embodiment of the present disclosure will be described with
reference to the attached drawings. In the following descriptions
and drawings, constituent elements shared by a plurality of
drawings are denoted by the same reference signs. Thus, after
constituent elements shared by a plurality of drawings are
described, descriptions of the constituent elements denoted by the
same reference signs will be appropriately omitted.
First Example Embodiment
A first embodiment relates to an example in which the electronic
device is an organic light emitting device. FIG. 1 is a schematic
sectional view of an organic light emitting device 100 according to
the first embodiment of the present disclosure. FIG. 2 is a top
view of the organic light emitting device 100. A section taken
along line I-I in FIG. 2 corresponds to FIG. 1. Three elements 10
constitute a single pixel. In this embodiment, such pixels are
arranged in a delta array serving as a non-limiting example.
Alternatively, the pixels may be arranged in a stripe array or a
square array.
The organic light emitting device 100 includes a substrate 1 and a
plurality of light emitting elements 10 disposed on the upper
surface (first surface) of the substrate 1. FIG. 1 illustrates,
among the plurality of light emitting elements 10 included in the
organic light emitting device 100, three light emitting elements
10R, 10G, and 10B. The symbol "R" of 10R means that the element is
configured to emit red light. Similarly, 10G and 10B respectively
denote elements configured to emit green light and blue light. In
this Specification, in the case of referring to, among the
plurality of light emitting elements 10, a specific light emitting
element, the reference number 10 is suffixed with a reference
character, for example, a light emitting element 10"R";
alternatively, in the case of generally referring to any light
emitting element 10, the element is simply referred to as a light
emitting element "10". The same applies to other constituent
elements.
The plurality of light emitting elements 10 include, in ascending
order from the upper surface of the substrate 1, lower electrodes 2
(first electrodes) divided by an insulating layer 3 so as to
correspond to light emitting elements; an organic layer 4 including
a light emitting layer covering the lower electrodes 2 and the
insulating layer 3; and an upper electrode 5 (second electrode)
covering the organic layer 4. The organic light emitting device 100
according to this embodiment is a top emission device configured to
extract light from the upper electrode 5. The organic light
emitting device 100 further includes a protective layer 6 disposed
so as to cover the upper electrode 5, and a plurality of color
filters 7 disposed on the protective layer 6 so as to individually
correspond to the plurality of light emitting elements 10. In this
embodiment, the organic layer 4 emits white light, and color
filters 7R, 7G, and 7B separate the white light emitted from the
organic layer 4 into RGB components, respectively. Alternatively,
the color filters may be color conversion layers configured to
absorb light from the organic layer and convert its color to other
colors. In case where the lower electrode comprises a plurality of
lower electrodes, the plurality of the lower electrodes may
comprise a first lower electrode and a second lower electrode.
In this Specification, the terms "upper" and "lower" respectively
denote upper and lower in FIG. 1. Of the main surfaces of the
substrate 1, a surface on which the lower electrodes 2 and other
constituent elements are disposed is referred to as the "upper"
surface. The term "height" is basically a distance measured upward
from the upper surface (first surface) of the substrate 1.
Alternatively, the "height" may be defined relative to a portion
level with the upper surface (first surface) of the substrate
1.
In FIG. 1, the reference sign 1 denotes a constituent element
simply referred to as a substrate; the substrate may be an
insulator disposed between the first electrode and a drive circuit
including a transistor connected to the first electrode. The
insulator is, for example, an interlayer insulating layer formed of
an inorganic substance such as silicon oxide or silicon nitride or
an organic substance such as polyimide or polyacrylate. The
interlayer insulating layer may also be referred to as a
planarization layer because it is used to reduce irregularities of
the surface on which the first electrodes are to be formed.
The lower electrodes 2 may be formed of a metal material having a
reflectance of 80% or more for the emission wavelength of the
organic layer 4. For example, the lower electrodes 2 may be formed
of a metal such as Al or Ag, or an alloy of the foregoing metal
containing, for example, Si, Cu, Ni, or Nd. The term "emission
wavelength" means the spectral range of light emitted from the
organic layer 4. As long as the lower electrodes 2 have a high
reflectance for the emission wavelength of the organic layer 4, the
lower electrodes 2 may have a stack structure including a barrier
layer. The barrier layer may be formed of a metal such as Ti, W,
Mo, or Au or an alloy of the foregoing metal. The barrier layer may
be a metal layer disposed at the upper surface of such a lower
electrode. The upper surface of a lower electrode 2R is a
reflection surface 12R. The reflection surface may reflect light
emitted from the organic layer. Similarly, the other pixels include
12G and 12B.
The insulating layer 3 may be disposed between the lower electrode
and the functional layer so as to cover an edge of the lower
electrode. The lower electrode may include a first region covered
with the insulating layer, and a second region not covered with the
insulating layer but covered with the organic layer. Stated another
way, the second region is in contact with the organic layer. The
second region is also referred to as an opening. This is because,
in a top view, the second region can be regarded as a recess formed
using the insulating layer. Such second regions serve as light
emission areas of the light emitting elements 10. Thus, when viewed
from the top, the shape of such a light emission area may be
defined by the insulating layer. The insulating layer is not
limited to the shape illustrated in FIG. 1 as long as it achieves
insulation among the first electrodes of the light emitting
elements.
The insulating layer 3 may include, in its upper portion, a slope
portion. This upper portion is positioned on the side opposite from
the substrate, in other words, on the side closer to the functional
layer.
The insulating layer 3 may be formed by, for example, chemical
vapor deposition (CVD) or physical vapor deposition (PVD). The
insulating layer 3 may be formed of, for example, silicon nitride
(SiN), silicon oxynitride (SiON), or silicon oxide (SiO). The
insulating layer 3 may be a stack of films formed of such
materials. The slope angle of the slope portion of the insulating
layer may be controlled by adjusting conditions of anisotropic
etching or isotropic etching. The slope angle of a layer
immediately below the insulating layer 3 may be controlled, to
thereby control the slope angle in the insulating layer 3. The
insulating layer 3 may have, in its upper surface, irregularities
formed by, for example, processing such as etching or stacking of
another layer.
The organic layer 4 is disposed between the lower electrode 2 and
the upper electrode 5. The organic layer 4 may be continuously
formed on the upper surface of the substrate 1, and shared by the
plurality of light emitting elements 10. Stated another way, the
single organic layer is shared by the plurality of light emitting
elements. The organic layer 4 may be formed as a single layer over
the whole surface of the display area for displaying images in the
organic light emitting device 100. The organic layer 4 may include
a hole transport layer, a light emitting layer, and an electron
transport layer. The material for the organic layer 4 can be
appropriately selected in accordance with a viewpoint such as light
emission efficiency, operating lifetime, or optical interference.
The hole transport layer may also function as an electron blocking
layer or a hole injection layer, or may be provided as a stack
structure of a hole injection layer, a hole transport layer, and an
electron blocking layer, for example. The light emitting layer may
have a stack structure of light emitting layers configured to emit
light of different colors, or may be a mixture layer including a
mixture of emission dopants configured to emit light of different
colors.
The electron transport layer may also function as a hole blocking
layer or an electron injection layer, or may have a stack structure
of an electron injection layer, an electron transport layer, and a
hole blocking layer.
A region between the light emitting layer and one of the upper
electrode and the lower electrode functioning as an anode serves as
a hole transport region; and a region between the other electrode
functioning as a cathode and the light emitting layer serves as an
electron transport region. The hole transport region and the
electron transport region are collectively referred to as a charge
transport region.
The organic light emitting device 100 may include a plurality of
light emitting layers, and may include an intermediate layer
between the plurality of light emitting layers. The organic light
emitting device 100 may be an organic light emitting device having
a tandem structure in which the intermediate layer is a charge
generating layer. In the tandem configuration, a transport layer
such as a hole transport layer or an electron transport layer may
be formed between the intermediate layer and such a light emitting
layer.
The upper electrode 5 is disposed on the organic layer 4. The upper
electrode 5 is continuously formed over a plurality of elements,
and is shared by the plurality of light emitting elements 10. As
with the organic layer 4, the upper electrode 5 may be formed as a
single layer over the whole surface of the display area for
displaying images in the organic light emitting device 100. The
upper electrode 5 may be an electrode that transmits at least a
portion of light having reached the lower surface of the upper
electrode 5. The upper electrode may function as a
semi-transmissive reflective layer that transmits a portion of
light and reflects the other portion (namely, semi-transmissive
reflectivity). The upper electrode 5 may be formed of, for example,
a metal such as magnesium or silver, an alloy including magnesium
or silver as a main component, or an alloy material including an
alkali metal or an alkaline earth metal. Alternatively, the upper
electrode 5 may be formed of an oxide conductor, for example.
Alternatively, the upper electrode 5 may have a stack structure as
long as it has an appropriate transmittance.
The protective layer 6 may be formed of, for example, a material
having a low permeability to external oxygen or moisture, such as
silicon nitride, silicon oxynitride, aluminum oxide, silicon oxide,
or titanium oxide. The silicon nitride and silicon oxynitride may
be formed by, for example, CVD. On the other hand, the aluminum
oxide, silicon oxide, and titanium oxide may be formed by atomic
layer deposition (ALD). The combination of the material and the
production method for the protective layer is not limited to the
above-described examples. The protective layer may be produced in
consideration of, for example, the thickness of the layer to be
formed, and the time for the formation. The protective layer 6 may
have a monolayer structure or a stack structure as long as it
transmits light having passed through the upper electrode 5, and
has sufficiently high moisture barrier performance.
The color filters 7 are formed over the protective layer 6. As
illustrated in FIG. 1, the color filters 7 may be in contact with
each other without gaps, such as a color filter 7R and a color
filter 7G. Alternatively, a color filter may be disposed so as to
overlap a color filter of another color. The color filters may have
a planarization layer 8 between the protective layer and the color
filters. The color filters may have another planarization layer
over the color filters. The planarization layer over the color
filters and the planarization layer under the color filters may be
formed of the same material. Examples of the material for these
planarization layers include acrylic resins, epoxy resins, and
polyimide resins.
The organic layer 4 above the lower electrode 2R has a layer
thickness C, which is the thickness of the organic layer measured
in a direction perpendicular to the lower electrode. A distance D
from the opening of the lower electrode 2R to the opening of the
lower electrode 2G is the shortest distance between edges of the
openings.
An electronic device according to an embodiment of the present
disclosure may have a ratio of the distance between the opening of
a first electrode to the opening of a neighboring first electrode
to the layer thickness of the organic layer on the first
electrodes, the ratio being less than 50. Such an organic light
emitting device that satisfies this numerical range is a device in
which the light emitting elements are arranged at such a high
density that leakage current between the light emitting elements
can pose a problem. The reason for this is as follows.
FIG. 3 is a schematic view of an organic light emitting device
including a light emitting element 10R provided with a red color
filter 7R and a light emitting element 10G provided with a green
color filter 7G. The difference from FIG. 1 is that the insulating
layers do not have the slope portions, so that a reduction in the
leakage current between elements is not achieved. The equivalent
circuit of the light emitting element 10R is superimposed on the
schematic view. The equivalent circuit indicates the resistance of
the organic layer in FIG. 3, but does not indicate incorporation of
the electronic circuit. In addition, in order to explain the
leakage current between the light emitting elements, the equivalent
circuit of the light emitting element 10G is also illustrated.
When the thickness of the organic layer on the lower electrode 2R
is denoted by C, the distance between the openings of the lower
electrode 2R and the lower electrode 2G is denoted by D, and a
resistance (in the thickness direction) per unit area of the
organic layer is denoted by r, a resistance (in the horizontal
direction) per unit area of the organic layer is expressed by
r(D/C). In this case, when a current flowing through the light
emitting element 10R is denoted by I.sub.R, and a current flowing
through the light emitting element 10G is denoted by I.sub.G, the
following relation holds. I.sub.G/I.sub.R=1/(1+D/C) (2)
Specifically, even in the case of trying to cause emission 9R only
from the red light emitting element 10R, current also flows through
the green light emitting element 10G to cause emission 9G, which
depends on D/C.
In the case of causing, with the same amount of current, emission
from the red light emitting element 10R and emission from the green
light emitting element 10G where the emission spectrum of the red
light emitting element 10R alone is denoted by S.sub.R and the
emission spectrum of the green light emitting element 10G alone is
denoted by S.sub.G, an emission spectrum S.sub.R+G in consideration
of the leakage current between the light emitting elements is
expressed by the following Formula (3).
S.sub.R+G=S.sub.R+S.sub.G(I.sub.G/I.sub.R) (3)
The chromaticity coordinates of S.sub.R+G in CIExy space are
calculated, and a graph in which the x value is plotted on the
ordinate, and D/C is plotted on the abscissa is illustrated in FIG.
4. In FIG. 4, the x-coordinate varies, which means that, in
addition to the intended emission of red light, green light is also
emitted. Thus, in FIG. 4, the x-coordinate that is small means
flowing of leakage current to the neighboring pixel. When D/C is 50
or more, the x value substantially does not vary. Specifically,
even in the case where the insulating layers do not have the slope
portions and leakage current tends to flow between light emitting
elements, when D/C is 50 or more, the leakage current between light
emitting elements may not pose a problem. On the other hand, when
D/C is less than 50, the x value considerably decreases, so that
the red color purity decreases noticeably; this case corresponds to
an organic light emitting device in which light emitting elements
are arranged at such a high density that leakage current between
light emitting elements can pose a problem. Thus, in such a case
where D/C is less than 50, the organic light emitting device
according to this embodiment provides a particularly strong effect
of reducing leakage current.
The optical distance between a pair of electrodes of an organic
light emitting device according to an embodiment of the present
disclosure may provide a constructive interference structure. The
constructive interference structure can also be referred to as a
resonance structure.
In the light emitting elements, organic layers can be formed so as
to satisfy constructive optical interference conditions, so that
optical interference provides enhanced extraction light from the
organic light emitting device. When optical conditions for
providing enhanced extraction light in the front direction are
satisfied, light is radiated in the front direction at higher
efficiency. Light enhanced by optical interference is known to have
an emission spectrum having a smaller half width than the
pre-interference emission spectrum. Thus, a higher color purity is
achieved. In designing of the organic light emitting device for
light of wavelength .lamda., a distance do from the emission
position of the light emitting layer to the reflection surface of
the reflective material is adjusted so as to satisfy
d.sub.0=i.lamda./4n.sub.0 (i=1, 3, 5, etc.) to thereby provide
constructive interference.
This results in an increase in the amount of front direction
component in the emission distribution of light of wavelength
.lamda., which results in an increase in the front luminance
Incidentally, no represents the refractive index (for wavelength
.lamda.) of a layer from the emission position to the reflection
surface.
An optical distance Lr from the emission position to the reflection
surface of the light reflective electrode is expressed by the
following Formula (4) where the sum of phase shift amount upon
reflection of light of wavelength .lamda. at the reflection surface
is denoted by .PHI.r [rad]. Incidentally, the optical distance L is
the sum of the product of the refractive index nj and thickness dj
of each layer of the organic layer. Thus, L can be expressed by
.SIGMA.nj.times.dj, or by n0.times.d0. Incidentally, .PHI. is a
negative value. Lr=(2m-(.PHI.r/.pi.)).times.(.lamda./4) (4)
In Formula (4) above, m is an integer of 0 or more. Incidentally,
in the case of .PHI.=-.pi., m=0 results in L=.lamda./4, and m=1
results in L=3.lamda./4. Hereafter, the condition of m=0 in Formula
(4) above will be referred to as the .lamda./4 interference
condition, and the condition of m=1 in Formula (4) above will be
referred to as the 3.lamda./4 interference condition.
An optical distance Ls from the emission position to the reflection
surface of the light extraction electrode is expressed by the
following Formula (5) where the sum of phase shift upon reflection
of light of wavelength .lamda. at the reflection surface is denoted
by .PHI.s [rad]. In the following Formula (5), m' is an integer of
0 or more.
Ls=(2m'-(.PHI.s/.pi.)).times.(.lamda./4)=-(.PHI.s/.pi.).times.(.lamda./4)
(5)
Thus, all layer interference L is expressed by the following
Formula (6). L=(Lr+Ls)=(2m-(.PHI./.pi.)).times.(.lamda./4) (6)
In this Formula, .PHI. represents the sum of phase shift
(.PHI.r+.PHI.s) upon reflection of light of wavelength .lamda. at
the light reflective electrode and at the light extraction
electrode.
In this case, actual light emitting elements are not necessarily
designed so as to strictly satisfy Formula (6) above in
consideration of, for example, viewing angle characteristics, which
are a trade-off for the front extraction efficiency. Specifically,
L may have errors of .+-..lamda./8 from the value satisfying
Formula (6). The allowable errors of L from the interference
condition may be 50 nm or more and 75 nm or less.
Thus, an organic light emitting device according to an embodiment
of the present disclosure preferably satisfies the following
Formula (7). More preferably, L is within .+-..lamda./16 from the
value satisfying Formula (6), preferably satisfies the following
Formula (7').
(.lamda./8).times.(4m-(2.PHI./.pi.)-1)<L<(.lamda./8).times.(4m-(2.P-
HI./.pi.)+1) (7)
(.lamda./16).times.(8m-(4.PHI./.pi.)-1)<L<(.lamda./16).times.(8m-(4-
.PHI./.pi.)+1) (7')
Light emitting elements according to an embodiment of the present
disclosure can satisfy, in Formula (7) and Formula (7'), m=0 and
m'=0, namely, the .lamda./4 optical interference condition. In this
case, Formula (7) and Formula (7') give Formula (8) and Formula
(8').
(.lamda./8).times.(-(2.PHI./.pi.)-1)<L<(.lamda./8).times.(-(2.PHI./-
.pi.)+1) (8)
(.lamda./16).times.(-(4.PHI./.pi.)-1)<L<(.lamda./16).times.(-(4.PHI-
./.pi.)+1) (8')
In Formula (7) and Formula (7'), when m=0 and m'=0, in the
constructive interference structure, the organic layer has the
smallest thickness. This results in a decrease in the driving
voltage of the light emitting elements, to thereby achieve emission
having higher luminance at a voltage below the upper limit of the
power supply voltage. When the organic layer has a smaller
thickness, leakage current tends to flow between the upper
electrode and the lower electrode; in this case, satisfying
features according to an embodiment of the present disclosure
provides a particularly stronger effect of reducing leakage current
between the upper electrode and the lower electrode.
The emission wavelength .lamda. may be the emission wavelength of a
peak having the highest emission intensity. In general, emission
from an organic compound has the highest intensity at the shortest
wavelength peak among peaks within the emission spectrum; thus, the
emission wavelength .lamda. may be the wavelength at the shortest
wavelength peak.
An electronic device according to an embodiment of the present
disclosure includes a functional layer having a small layer
thickness. More specifically, the functional layer has, on the
second region (of the first electrode) not covered with the
insulating layer, a layer thickness smaller than the height of the
insulating layer. The layer thickness of the functional layer can
be estimated not only on the second region of the first electrode,
but also on the upper surface of the insulating layer. In a device
including a functional layer having such a small layer thickness
that leakage current between elements can pose a problem, the
functional layer is formed so as to have, in a region extending
along the slope portion of the insulating layer, a layer thickness
of 20 nm or more. The phrase "functional layer extending along the
slope portion of the insulating layer" means a structure in which a
line drawn so as to be perpendicular to the slope portion of the
insulating layer reaches the slope portion of the functional
layer.
In summary, in an electronic device according to an embodiment of
the present disclosure, the functional layer on the second region
of the first electrode has a layer thickness smaller than the
height of the insulating layer, to thereby achieve a reduction in
the leakage current to neighboring elements. Simultaneously, the
functional layer on the slope portion of the insulating layer has a
layer thickness of 20 nm or more, to thereby achieve a reduction in
leakage current between the first electrode and the second
electrode.
FIG. 5A is an enlarged view of the dotted box VA in FIG. 1. FIG. 5A
illustrates a second region 21 of the first electrode and a slope
portion 31 of the insulating layer. The slope portion 31 of the
insulating layer is a slope portion on the first region of the
first electrode. The slope portion 31 can also be referred to as a
slope portion in contact with the light emission area, or a slope
portion forming the inner periphery of the opening. In plan view in
a direction perpendicular to the substrate, the slope portion and
the first region of the first electrode overlap. On the other hand,
a slope portion 32 is a slope portion disposed, in plan view in a
direction perpendicular to the substrate, between the first
electrode and another first electrode. The slope portion 32 can
also be referred to as a slope portion forming the outer periphery
of the opening, or a slope portion between pixels. On the second
region 21, a height F of the upper surface of the organic layer
denotes the height of the upper surface of the organic layer formed
substantially parallel to the second region 21. The organic layer
on the second region can also be referred to as a flat portion of
the organic layer on the first electrode.
An upper end 33 of the slope portion 31 of the insulating layer is
a point where the insulating layer has an angle of 0.degree.. The
height of the upper end 33 of the slope portion 31 is denoted by E.
The slope angle .theta. of the slope portion of the insulating
layer may be constant at any point of the slope portion as
illustrated in FIG. 5A; alternatively, the slope angle may vary
depending on points of the slope portion. Even in such a case where
the slope angle varies, regions having slope angles of more than
0.degree. are regarded as being included in the same slope portion;
points at both ends of the slope portion 31 where the slope angles
are 0.degree. are the upper end 33 and a lower end 34 of the slope
portion 31. In the case of the planar structure illustrated in FIG.
2, the slope portion 31 is continuously formed so as to extend
along all the sides of each hexagon.
The organic layer 4 has the upper surface having height F smaller
than height E of the upper end 33 of the slope portion 31. This is
because, in the organic light emitting device according to this
embodiment, the organic layer has a layer thickness smaller than
the height of the insulating layer. Specifically, as illustrated in
FIG. 5A, the organic light emitting device according to this
embodiment includes the organic layer extending along the slope
portion of the insulating layer. This forms a region 41 (within the
dotted box) of the organic layer extending along the slope portion
31. The region of the organic layer extending along the slope
portion is formed substantially parallel to the slope portion;
referring to the region 41 of the organic layer, this region is
defined by lines drawn perpendicular to the insulating layer. In
the case of the planar structure illustrated in FIG. 2, the region
41 of the organic layer extending along the slope portion 31
continuously extends along all the sides of each hexagon.
Incidentally, the phrase "substantially parallel" means the
following: when "parallel" is defined as a case where a slope angle
at a point on the slope portion is equal to a slope angle at the
upper surface of the organic layer 4 positioned where a line drawn
from the point so as to be perpendicular to the slope portion
intersects the upper surface of the organic layer 4, "substantially
parallel" is a case where the difference between the slope angles
is within the range of .+-.15.degree..
In FIG. 5A, a region 42 of the organic layer is not the organic
layer extending along the slope portion 31 of the insulating layer.
This is because the organic layer formed on the second region 21
has a large layer thickness, so that it conceals the organic layer
formed so as to extend along the slope portion 31.
FIG. 5B illustrates a comparative example in which the organic
layer 4 has the upper surface having height F larger than height E
of an upper end 33 of the slope portion 31. In this case, the
organic layer extending along the slope portion 31 is not present.
This is because the organic layer formed on the second region 21
has a large layer thickness, so that it conceals the organic layer
formed so as to extend along the slope portion 31. In the example
in FIG. 5B, the organic layer has a relatively low resistance, so
that leakage current flowing to neighboring light emitting elements
may not be sufficiently reduced.
The inventors of the present disclosure studied organic devices
having various configurations, and have found the following
findings: referring to FIG. 5A, when the organic layer has, on the
slope portion 31, a layer thickness G of 20 nm or more, leakage
current between the upper electrode 5 and the lower electrode 2 can
be considerably reduced. The layer thickness of the organic layer
on the slope portion is a layer thickness measured in a direction
perpendicular to the slope portion of the insulating layer. In
addition, the organic layer extending along the slope portion has a
smaller layer thickness than the organic layer formed on the flat
portion, hence has a high electric resistance. The organic layer on
the second region has a small layer thickness; in addition, the
slope portion is formed to achieve an increase in the resistance of
the organic layer. This results in a reduction in leakage current
flowing to the neighboring light emitting element. When the leakage
current flowing to the neighboring light emitting element is thus
reduced, occurrence of unintentional emission from the light
emitting element is reduced, to thereby reduce narrowing of the
color gamut of the light emitting apparatus. The organic layer on
the slope portion 31 preferably has a layer thickness G of 25 nm or
more, particularly preferably 33 nm or more. This achieves a
further reduction in the leakage current between the upper
electrode and the lower electrode.
Thus, the organic device illustrated in FIG. 5A achieves both of a
reduction in the leakage current flowing to neighboring light
emitting elements, and a reduction in the leakage current between
the upper electrode and the lower electrode. The layer thickness of
the organic layer measured in a direction perpendicular to the
slope portion may be 20 nm or more even in a portion having the
smallest layer thickness on the single slope portion. The layer
thickness of the organic layer measured in a direction
perpendicular to the slope portion can be controlled by adjusting,
for example, the slope angle of the slope portion or formation
conditions of the organic layer. The slope portion of the
insulating layer may have a slope angle of 50.degree. or less.
The organic light emitting device according to this embodiment
includes a plurality of insulating layers. One of such insulating
layers is described above as an example. On each of the plurality
of insulating layers, the organic layer on the slope portion may
have a layer thickness of 20 nm or more measured in a direction
perpendicular to the slope portion.
The layer thickness of the organic layer on the slope portion 31 of
the insulating layer has been described so far. Similarly, on the
slope portion 32 of the insulating layer, the layer thickness of
the organic layer measured in a direction perpendicular to the
slope portion can be 20 nm or more. On both of the slope portions,
the organic layer can have a layer thickness of 20 nm or more. Of
these slope portions, a case where, on the slope portion 31, the
layer thickness is 20 nm or more is better than a case where, on
the slope portion 32, the layer thickness is 20 nm or more. This is
because, compared with the organic layer on the slope portion 32,
the organic layer on the slope portion 31 contributes to the
leakage current between the first electrode and the second
electrode.
On a slope portion (on a first region of the first electrode) of
each of a plurality of insulating layers, the layer thickness of
the organic layer measured in a direction perpendicular to the
slope portion may be 20 nm or more. On each slope portion of all
the insulating layers, the layer thickness of the organic layer
measured in a direction perpendicular to the slope portion may be
20 nm or more. On a slope portion (disposed between a first
electrode and another first electrode) of a plurality of insulating
layers, the layer thickness of the organic layer measured in a
direction perpendicular to the slope portion may be 20 nm or more.
On each slope portion (disposed between a first electrode and
another first electrode) of all the insulating layers, the layer
thickness of the organic layer measured in a direction
perpendicular to the slope portion may be 20 nm or more.
In the organic light emitting device according to this embodiment,
the slope surface of a slope portion is not parallel to the upper
surface of the first electrode; the slope surface of the slope
portion is, in the surface of the insulating layer, a region
positioned between the upper surface of the insulating layer and
the upper surface of the first electrode covered with the
insulating layer. Stated another way, the slope surface of the
slope portion is, in the surface of the insulating layer, a region
positioned between the edge of the upper surface of the insulating
layer, and the upper surface of the first electrode. The slope
portion on the first electrode may have an angle of less than
90.degree.. In the case where the angle is less than 90.degree., in
the upward direction from the upper surface of the first electrode,
the width of the opening defined by the insulating layer
increases.
Second Example Embodiment
FIG. 6 relates to a second embodiment according to the present
disclosure. The second embodiment is the same as the first
embodiment except that the insulating layer 3 has a different
shape, and the organic layer includes, in a lower portion, a charge
transport region. Hereinafter, the differences from the first
embodiment and the resultant advantages will be described.
A slope portion 31 (on the first region of the first electrode) of
the insulating layer includes a gentle slope portion (thick line
portion) 311 and a steep slope portion (thick line portion) 312.
The gentle slope portion is disposed, in the slope portion, between
the upper end of the slope portion and the lower end of the slope
portion. When the insulating layer has an upper surface, the height
of the upper surface is equal to the height of the upper end; the
upper surface itself is not included in the upper end. The steep
slope portion is disposed between the gentle slope portion and the
lower end of the slope portion. More specifically, the steep slope
portion is disposed between the lower end of the gentle slope
portion and the lower end of the slope portion.
In FIG. 6, the gentle slope portion 311 is, in the slope portion
31, a portion in contact with a region 41 of the organic layer
extending along the slope portion. The gentle slope portion is
formed at an angle .theta.1 relative to the upper surface of the
first electrode. When the upper surface of the first electrode is
parallel to the horizontal plane, the angle of the gentle slope
portion may be .theta.1 relative to the horizontal plane. The steep
slope portion is disposed between the gentle slope portion and the
lower end of the insulating layer, and is formed at an angle
.theta.2 relative to the upper surface of the first electrode. The
steep slope portion 312 is, in the slope portion 31, a portion
having the slope angle .theta.2 larger than the largest slope angle
.theta.1 in the gentle slope portion 311.
The steep slope portion has a slope angle .theta.2 of more than
50.degree.. The gentle slope portion has a slope angle .theta.1 of
50.degree. or less. The steep slope portion can have a slope angle
.theta.2 of more than 50.degree. and 90.degree. or less. The gentle
slope portion can have a slope angle .theta.1 of 30.degree. or more
and 50.degree. or less.
The organic layer 4 is constituted by a charge transport layer 43
and a region 44 including a light emitting layer; the charge
transport layer is disposed on the first-electrode side of the
organic layer 4. In the charge transport layer, the constituent
component of the organic layer may be different from that of the
organic layer. On the second region 21 of the first electrode, the
charge transport layer has an upper surface 431 having height I
smaller than height H of the upper end of the steep slope portion
312. Thus, the charge transport layer 43 forms a region having a
small layer thickness in a direction perpendicular to the steep
slope portion, which is a region extending along the steep slope
portion 312.
In the case of forming the layer by vapor deposition, the larger
the slope angle of the slope portion, the smaller the layer
thickness of the resultant layer extending along the slope portion.
This tends to result in an increase in the resistance of the charge
transport layer. The charge transport layer is, in the organic
layer, a region having a high charge transport capability, so that
it tends to contribute to leakage current between light emitting
elements. However, when the charge transport layer is formed with
increased resistance as described above, leakage current between
light emitting elements can be reduced.
Thus, on the second region 21 of the first electrode, the organic
layer is formed so as to have an upper surface having height F
larger than height H of the upper end of the steep slope portion
312. In this way, the organic layer 4 on the second region 21 has a
region with increased resistance provided by formation of the steep
slope portion.
Even when the insulating layer including the slope portion provides
the thin region of the organic layer, in the organic light emitting
device according to this embodiment, the organic layer on the slope
portion has a layer thickness of 20 nm or more in a direction
perpendicular to the slope portion. This achieves a reduction in
the leakage current between the first electrode and the second
electrode.
The gentle slope portion and the steep slope portion according to
this embodiment can be formed in the following manner. For example,
the gentle slope portion 311 can be formed by isotropic etching,
and the steep slope portion 312 can be formed by anisotropic
etching.
The case where the slope portion 31 of the insulating layer
includes a gentle slope portion and a steep slope portion has been
described so far as an example. A slope portion 32 of the
insulating layer may include a gentle slope portion and a steep
slope portion.
The steep slope portion and gentle slope portion of the insulating
layer may each have a slope angle that is constant as illustrated
in FIG. 6. Alternatively, the slope angle may vary along the slope
portion. In this case, the boundary between the gentle slope
portion and the steep slope portion is a point at which the slope
angle exceeds 50.degree..
The charge transport layer according to this embodiment may be a
hole transport layer. In general, a hole transport layer has a
higher charge mobility than an electron transport layer. When such
a hole transport layer is employed for this embodiment, a hole
transport layer can be formed with increased resistance, to thereby
provide a stronger effect of reducing the leakage current between
light emitting elements. The hole transport layer may be a hole
transport region constituted by a plurality of organic compound
layers.
In the case of reducing the leakage current between light emitting
elements, the light emitting layer can be of an electron trap type.
The electron trap type means a light emitting layer in which,
relative to the energy of the lowest unoccupied molecular orbital
of the host material serving as the main component of the light
emitting layer, the energy of the lowest unoccupied molecular
orbital of a dopant material included in the light emitting layer
is deep by 0.15 eV or more. This results in a decrease in the
electron mobility of the light emitting layer. Thus, the leakage
current between light emitting elements due to holes can be
addressed by the increased resistance provided by the slope
portion; the leakage current between light emitting elements due to
electrons can be addressed by the increased resistance provided by
the light emitting layer. This facilitates a reduction in both of
leakage current between light emitting elements due to holes and
leakage current between light emitting elements due to
electrons.
In order to find desirable slope angles of the slope portion in
this embodiment, simulation of film formation by vapor deposition
was performed. FIG. 7 illustrates members disposed during the vapor
deposition simulation. An evaporation source 201, a substrate 202,
and an organic device 203 disposed on the substrate are positioned
as illustrated in FIG. 7 such that R=200 mm, r=95 mm, and h=340
mm.
The simulation was performed with a vapor deposition distribution
represented by the following Formula (9) where n=2.
.PHI.=.PHI..sub.0 cos.sup.n .alpha. (9)
In this formula, .alpha. represents angle, .PHI. represents vapor
stream density at angle .alpha., and .PHI..sub.0 represents vapor
stream density when .alpha.=0. The substrate 202 was defined to be
rotated at the center of the substrate.
At the position of the organic device 203 on the substrate, a slope
portion having a slope angle of 0.degree. to 90.degree. was assumed
to be disposed. While the layer thickness of the organic layer at a
slope angle of 0.degree. was set to 76 nm, the layer thicknesses of
regions of the organic layers extending along the slope portions at
different slope angles were calculated.
FIG. 8 illustrates the results of the simulation of film formation.
This has demonstrated the following: when the slope angle is more
than 50.degree., the region of the organic layer extending along
the slope portion tends to have a small layer thickness; when the
slope angle is 50.degree. or less, the region of the organic layer
extending along the slope portion tends to have a large layer
thickness. Thus, in this embodiment, the steep slope portion can be
formed to have a slope angle of more than 50.degree., and the
gentle slope portion can be formed to have a slope angle of
50.degree. or less.
In this embodiment, the steep slope portion may include a portion
having a slope angle of more than 90.degree.. In this case, in
particular, the charge transport layer on the steep slope portion
tends to have a small layer thickness, which tends to result in a
reduction in the leakage current between light emitting
elements.
Applications of Organic Light Emitting Device According to This
Embodiment
The organic light emitting device according to this embodiment can
be used as a constituent member for a display apparatus or an
illumination apparatus, and is also applicable to the exposure
light source of an electrophotographic image-forming apparatus, the
backlight of a liquid crystal display apparatus, or a light
emitting apparatus in which a white light source is equipped with a
color filter.
The display apparatus may be an image information processing
apparatus including an image input section configured to input
image information from, for example, an area CCD, a linear CCD, or
a memory card, and an information processing section configured to
process the inputted information, and configured to display the
inputted image on a display unit.
An image pickup apparatus or an ink jet printer may have a display
unit having a touch panel function. The operation type of this
touch panel function is not particularly limited, and may be an
infrared type, a capacitance type, a resistive film type, or an
electromagnetic induction type. The display apparatus may be used
as a display unit of a multifunctional printer.
Hereinafter, a display apparatus according to an embodiment will be
described. The display apparatus may include an organic light
emitting device and a transistor connected to the organic light
emitting device. The transistor is an example of an active
device.
The transistor may be connected, via a contact hole formed in the
interlayer insulating layer, to the first electrode constituting
the organic light emitting device.
Incidentally, the configuration of electric connections of
electrodes (anode and cathode) included in the organic light
emitting device and electrodes (source electrode and drain
electrode) included in the transistor is not particularly limited.
In other words, any configuration may be employed as long as one of
the anode and the cathode is electrically connected to one of the
source electrode and the drain electrode of the transistor.
In the display apparatus, the transistors are not limited to
transistors using a single-crystal silicon wafer, and may be
thin-film transistors having an active layer on the insulating
surface of the substrate. The active layer may be formed of
single-crystal silicon, a non-single-crystal silicon such as
amorphous silicon or microcrystal silicon, or a non-single-crystal
oxide semiconductor such as indium zinc oxide or indium gallium
zinc oxide. Incidentally, thin-film transistors are also referred
to as TFT.
The transistors included in the display apparatus may be formed
within the substrate such as a Si substrate. The phrase "formed
within the substrate" means that the substrate itself such as a Si
substrate is processed to form transistors. In other words, the
configuration in which transistors are included within the
substrate can be regarded as a configuration in which the substrate
and the transistors are formed as a single unit.
The organic light emitting device according to this embodiment is
controlled, in terms of emission luminance, by TFTs as examples of
switching devices. A plurality of such organic light emitting
devices are arranged in a plane, to emit light at individual
emission luminances to thereby display images. Incidentally,
whether transistors are formed within the substrate or TFTs are
formed depends on the size of the display unit. For example, when
the display unit has a size of about 0.5 inches, the organic light
emitting device can be formed on a Si substrate.
FIG. 9 is a schematic view illustrating an example of a display
apparatus according to an embodiment. A display apparatus 1000 may
include, between an upper cover 1001 and a lower cover 1009, a
touch panel 1003, a display panel 1005, a frame 1006, a circuit
substrate 1007, and a battery 1008. To the touch panel 1003 and the
display panel 1005, flexible printed circuit FPCs 1002 and 1004 are
respectively connected. On the circuit substrate 1007, transistors
are formed by printing. The battery 1008 may not be installed when
the display apparatus is not a mobile apparatus. When the display
apparatus is a mobile apparatus, the battery 1008 may be installed
in another position.
A display apparatus according to this embodiment may be used as a
display unit of an image pickup apparatus including an optical unit
including a plurality of lenses and an image pickup device
configured to receive light having passed the optical unit. The
image pickup apparatus may include a display unit configured to
display information obtained by the image pickup device. The
display unit may be a display unit exposed outside of the image
pickup apparatus, or a display unit disposed within the finder. The
image pickup apparatus may be a digital camera or a digital video
camera.
FIG. 10A is a schematic view illustrating an example of an image
pickup apparatus according to an embodiment. An image pickup
apparatus 1100 may include a view finder 1101, a rear surface
display 1102, an operation unit 1103, and a housing 1104. The view
finder 1101 may include the display apparatus according to this
embodiment. In this case, the display apparatus may display not
only an image to be captured, but also, for example, environmental
information and image capture instructions. Examples of the
environmental information include the intensity of external light,
the orientation of external light, the moving speed of the subject,
and the probability that the subject may hide behind an
obstacle.
Since the timing suitable for capturing an image lasts for a very
short period, the information is desirably displayed with minimum
delay. Thus, a display apparatus employing an organic light
emitting device according to an embodiment of the present
disclosure can be used because the organic light emitting device
responds at a high speed. The display apparatus employing the
organic light emitting device can be more suitably used for such
image pickup apparatuses required to display images at high speed
than liquid crystal display apparatuses.
The image pickup apparatus 1100 includes an optical unit (not
shown). The optical unit includes a plurality of lenses and is
configured to form an image in the image pickup device contained
within the housing 1104. The plurality of lenses can be adjusted in
terms of relative positions, to thereby adjust the focus. This
operation can also be performed automatically.
The display apparatus according to this embodiment may include red,
green, and blue color filters. These red, green, and blue color
filters may be arranged in a delta array.
The display apparatus according to this embodiment may be used for
a display unit of a portable terminal. In this case, the display
apparatus may have both of a display function and an operation
function. Examples of the portable terminal include cellular phones
such as smartphones, tablets, and head mount displays.
FIG. 10B is a schematic view illustrating an example of an
electronic apparatus according to an embodiment. An electronic
apparatus 1200 includes a display unit 1201, an operation unit
1202, and a housing 1203. The housing 1203 may include circuits, a
printed substrate including the circuits, a battery, and a
communication unit. The operation unit 1202 may be a button or a
touch-panel-type sensor unit. The operation unit may be a biometric
unit configured to scan a fingerprint for unlocking, for example.
Such an electronic apparatus including a communication unit can
also be referred to as a communication apparatus.
FIGS. 11A and 11B are schematic views illustrating examples of a
display apparatus according to an embodiment. FIG. 11A illustrates
a display apparatus such as a television monitor or a PC monitor. A
display apparatus 1300 includes a frame 1301 and a display unit
1302. The display unit 1302 may employ the light emitting device
according to the embodiment.
The display apparatus includes a base 1303, which supports the
frame 1301 and the display unit 1302. The base 1303 is not limited
to the form illustrated in FIG. 11A. The lower side of the frame
1301 may also function as the base.
The frame 1301 and the display unit 1302 may be curved. The radius
of the curvature may be 5000 mm or more and 6000 mm or less.
FIG. 11B is a schematic view illustrating another example of the
display apparatus according to this embodiment. A display apparatus
1310 in FIG. 11B can be folded, namely a foldable display
apparatus. The display apparatus 1310 includes a first display unit
1311, a second display unit 1312, a housing 1313, and a folding
point 1314. The first display unit 1311 and the second display unit
1312 may include the light emitting device according to the
embodiment. The first display unit 1311 and the second display unit
1312 may be collectively designed as a seamless single display
apparatus. The first display unit 1311 and the second display unit
1312 can be sectioned with respect to the folding point.
Specifically, the first display unit 1311 and the second display
unit 1312 may individually display different images; and the first
and second display units may collectively display a single
image.
FIG. 12A is a schematic view illustrating an example of an
illumination apparatus according to an embodiment. An illumination
apparatus 1400 may include a housing 1401, a light source 1402, a
circuit substrate 1403, an optical film 1404, and a light diffusion
unit 1405. The light source may include the organic light emitting
device according to the embodiment. An optical filter may be
provided to improve color rendering of the light source. The light
diffusion unit is configured to effectively diffuse light from the
light source to deliver the light to a wide area, to achieve
lighting up, for example. The optical filter and the light
diffusion unit may be provided on the light exit side of the
illumination. The illumination may be optionally equipped with a
cover for the outermost portion thereof.
The illumination apparatus is, for example, an apparatus configured
to illuminate the inside of a room. The illumination apparatus may
be configured to emit light of any color of white, neutral white,
and colors from blue to red. The illumination apparatus may include
a light modulation circuit for modulating the light. The
illumination apparatus may include an organic light emitting device
according to an embodiment of the present disclosure and a power
supply circuit connected to the organic light emitting device. The
power supply circuit is configured to convert alternating current
voltage to direct current voltage. The "white" corresponds to a
color temperature of 4200 K. The "neutral white" corresponds to a
color temperature of 5000 K. The illumination apparatus may include
a color filter.
The illumination apparatus according to this embodiment may include
a heat dissipation unit. The heat dissipation unit is configured to
release heat inside of the apparatus to the outside of the
apparatus. The heat dissipation unit is formed of, for example, a
metal having a high specific heat or liquid silicone.
FIG. 12B is a schematic view of an automobile serving as an example
of a moving object according to an embodiment. The automobile
includes a tail lamp serving as an example of the illumination
unit. An automobile 1500 includes a tail lamp 1501 that may be
configured to turn on upon braking, for example.
The tail lamp 1501 may include the organic light emitting device
according to the embodiment. The tail lamp may include a protective
member for protecting the organic EL device. The material forming
the protective member is not limited as long as it has relatively
high strength and is transparent. The protective member can be
formed of polycarbonate, for example. The polycarbonate may be
mixed with, for example, a furandicarboxylic acid derivative or an
acrylonitrile derivative.
The automobile 1500 may include an automobile body 1503 and a
window 1502 attached to the automobile body 1503. When the window
is not windows for checking ahead or behind of the automobile, it
may be designed as a transparent display. This transparent display
may include the organic light emitting device according to the
embodiment. In this case, constituent members of the organic light
emitting device, such as electrodes, are provided as transparent
members.
The moving object according to this embodiment may be a ship, an
aircraft, or a drone, for example. The moving object may include a
body and an illumination unit provided to the body. The
illumination unit may emit light in order to indicate the position
of the body. The illumination unit includes the organic light
emitting device according to the embodiment.
As has been described so far, apparatuses employing the organic
light emitting device according to the embodiment enable displaying
of images with high quality for a long time with stability.
EXAMPLES
Example 1
Hereinafter, an example of the organic light emitting device 100
according to this embodiment will be described. On the substrate 1,
a metal layer is formed. Desired regions of the metal layer were
etched off using, for example, a mask pattern, to thereby form the
lower electrodes 2. Subsequently, the insulating layers 3 were
formed so as to cover the edges of the lower electrodes 2. In this
Example, the insulating layers 3 were formed of silicon oxide; each
insulating layer 3 was formed with a thickness of 80 nm measured on
the upper surface of such a lower electrode 2 in a direction
perpendicular to the upper surface of the substrate 1. After the
insulating layers 3 were formed, desired regions of the insulating
layers 3 were etched off using, for example, a mask pattern, to
thereby form openings 12. As illustrated in FIG. 6, each insulating
layer 3 was formed so as to have a gentle slope portion and a steep
slope portion. The gentle slope portion 311 had a slope angle of
40.degree., and the steep slope portion 312 had a slope angle of
80.degree.. The height of the upper end of the steep slope portion
312 was set to 50 nm relative to the second region (flat portion)
21 at the upper surface of the first electrode. The height of the
slope portion 31 was set to 80 nm relative to the second region
(flat portion) 21 of the first electrode. In the slope portion 32
of the insulating layer 3, the gentle slope portion 321 was formed
so as to have a slope angle of 40.degree., and the steep slope
portion 322 was formed so as to have a slope angle of 80.degree..
The height of the slope portion 32 was set to 80 nm relative to the
flat portion 22 between the first electrode and another first
electrode. In this Example, pixels were arranged in a delta array
in which adjacent openings 12 had a distance of 1.4 .mu.m
therebetween, and adjacent lower electrodes 2 had a distance of 0.6
.mu.m therebetween. As illustrated in FIG. 2, the pixels each
having a hexagonal shape were arranged in the delta array.
Subsequently, the organic layer 4 was formed. The organic layer was
formed so as to include, in the following order, a hole injection
layer, a hole transport layer, an electron blocking layer, a light
emitting layer having a double layer structure, an electron
transport layer, and an electron injection layer. On the substrate
1, the hole injection layer was first formed using a material
represented by the following Compound 1 to a thickness of 7 nm.
##STR00001##
Subsequently, the hole transport layer was formed using a material
represented by the following Compound 2 to a thickness of 5 nm, and
the electron blocking layer was formed using a material represented
by the following Compound 3 to a thickness of 10 nm. The light
emitting layer was formed so as to have a stack structure of two
layers. As a first light emitting layer, a light emitting layer was
formed so as to include a host material represented by the
following Compound 4, and an emission dopant represented by the
following Compound 5. The amount of the emission dopant was
adjusted so as to satisfy a weight ratio of 3%. The first light
emitting layer was formed with a layer thickness of 10 nm.
##STR00002##
Subsequently, as a second light emitting layer, a light emitting
layer was formed so as to include a host material represented by
Compound 4 above, and an emission dopant represented by the
following Compound 6. The amount of the emission dopant was
adjusted so as to satisfy a weight ratio of 1%. The second light
emitting layer was formed with a layer thickness of 10 nm. After
the light emitting layer having a double layer structure was
formed, the electron transport layer was formed using the following
Compound 7 to a thickness of 34 nm. Furthermore, the electron
injection layer was formed using LiF to a thickness of 0.5 nm.
##STR00003##
After the organic layer 4 was formed, the upper electrode 5 was
formed using a MgAg alloy having a Mg--Ag ratio of 1:1 to a
thickness of 10 nm. After the upper electrode 5 was formed, a
sealing layer 6 was formed using SiN by CVD to a thickness of 1.5
.mu.m. After this protective layer 6 was formed, the color filters
7 were formed.
The ratio of the distance (1.4 .mu.m) between openings of two
adjacent first electrodes to the layer thickness (76 nm, total
thickness of the organic sublayers) of the organic layer on the
first electrodes was 18, which was less than 50. On the second
region (flat portion) 21 of such a first electrode, the organic
layer had a layer thickness of 76 nm, which was smaller than the
height (80 nm) of the upper end of the slope portion 31. On the
flat portion 22, the organic layer had a layer thickness of 76 nm,
which was smaller than the height (80 nm) of the upper end of the
slope portion 32. The region 41 of the organic layer extending
along the slope portion 31, and the region 42 of the organic layer
extending along the slope portion 32 had organic layer thicknesses
of 36 nm to 45 nm, which were 20 nm or more. Among the peaks in the
emission spectrum of the light emitting layer, a peak at the
shortest wavelength .lamda. was found at 460 nm; the optical
distance L was found to be 146 nm; and the phase shift .PHI. was
found to be -.pi.. Thus, the following Formula (5) was satisfied.
(.lamda./8).times.(-(2.PHI./.pi.)-1)<L<(.lamda./8).times.(-(2.PHI./-
.pi.)+1) (5)
The organic layer includes, between the first electrode and the
light emitting layer, a hole transport region constituted by the
hole injection layer and the hole transport layer. The charge
transport region on the flat portion 21 has an upper surface having
a height (relative to the flat portion 21) of 12 nm, which is
smaller than the height (50 nm) of the upper end of the steep slope
portion. The organic layer on the flat portion 21 has an upper
surface having a height (relative to the flat portion 21) of 76 nm,
which is larger than the height (50 nm) of the upper end of the
steep slope portion 312. Similarly, the charge transport region on
the flat portion 22 has an upper surface having a height (relative
to the flat portion 22) of 12 nm, which is smaller than the height
(50 nm) of the upper end of the steep slope portion. The organic
layer on the flat portion 22 has an upper surface having a height
(relative to the flat portion 22) of 76 nm, which is larger than
the height (50 nm) of the upper end of the steep slope portion
322.
Hereinafter, characteristics of the organic light emitting device
100 formed in Example 1 will be described. First, regarding an
index of leakage current between light emitting elements,
I.sub.leak/I.sub.oled, a method of measuring this index will be
described with reference to an R pixel as an example. Current is
passed through the R pixel while G pixels and B pixels adjacent to
the R pixel are short-circuited (potential=0 V). In this case, the
current passing from the first electrode of the R pixel to the
second electrode of the R pixel was denoted by I.sub.oled; the sum
of current passing from the first electrode of the R pixel to the
second electrodes of G pixels or B pixels was denoted by
I.sub.leak. I.sub.leak was measured at a potential providing an
I.sub.oled of 0.1 nA/pixel. The ratio of I.sub.leak to I.sub.oled
is expressed by I.sub.leak/I.sub.oled. Cases where the
I.sub.leak/I.sub.oled was 0.20 or less were evaluated as achieving
a reduction in the leakage current.
Second, the leakage current between the upper electrode and the
lower electrode will be described. Organic light emitting elements
have an emission threshold voltage of about 2 V. Thus, in a light
emitting element in which leakage current does not flow between the
upper electrode and the lower electrode, when a voltage such as 1.5
V is applied between the upper electrode and the lower electrode,
current does not flow. By contrast, in a light emitting element in
which leakage current flows between the upper electrode and the
lower electrode, when the voltage of 1.5 V is applied between the
upper electrode and the lower electrode, current flows. Thus, a
current value was measured while the voltage of 1.5 V was applied
between the upper electrode and the lower electrode of the R pixel.
Specifically, the current flowing upon application of 1.5 V is
leakage current. In a light emitting element in which a reduction
in the leakage current between the upper electrode and the lower
electrode is achieved, current does not flow upon application of
1.5 V.
Subsequently, while a voltage of 5 V was applied between the upper
electrode and the lower electrode of the R pixel, a current value
and a luminance were measured.
As a result, I.sub.leak/I.sub.oled was found to be 0.15; the amount
of current upon application of a voltage of 1.5 V was found to be
1.times.10.sup.-6 nA/pixel; the amount of current upon application
of a voltage of 5 V was found to be 16 nA/pixel; the luminance was
found to be 250 cd/m.sup.2. Thus, device characteristics including
the high luminance were obtained.
Comparative Example 1
An organic light emitting device was produced as in Example 1
except that the height of the steep slope portion 312 relative to
the flat portion 21 was set to 90 nm, the height of the slope
portion 31 relative to the flat portion 21 was set to 120 nm, the
height of the steep slope portion 322 relative to the flat portion
22 was set to 90 nm, and the height of the slope portion 32
relative to the flat portion 22 was set to 120 nm. The region 41 of
the organic layer extending along the slope portion 31 was formed
so as to extend along, in addition to the gentle slope portion 311,
the steep slope portion 312. The organic layer extending along the
steep slope portion was found to have thicknesses of 18 to 24 nm.
The same applied to the slope portion 32.
As a result, an excessively large leakage current flowed between
the upper electrode and the lower electrode, so that
I.sub.leak/I.sub.oled was not accurately measured. Specifically,
I.sub.leak was large and I.sub.oled was small, so that the
resultant I.sub.leak/I.sub.oled was a very large value and hence
unmeasurable. The amount of current upon application of a voltage
of 1.5 V was found to be 1.times.10.sup.-1 nA/pixel, which was very
large. At the inner periphery of the opening, a phenomenon of a
decrease in the intensity of emission occurred. This was
inferentially caused because the leakage current between the upper
electrode and the lower electrode results in a region subjected to
a decrease in the potential difference between the upper electrode
and the lower electrode.
This has demonstrated the following: when a region of the organic
layer extending along the slope portion has a portion having a
layer thickness of less than 20 nm, a large leakage current flows
between the upper electrode and the lower electrode.
Comparative Example 2
An organic device was produced as in Example 1 except that the
height of the steep slope portion 312 relative to the flat portion
21 was set to 30 nm and the height of the slope portion 31 relative
to the flat portion 21 was set to 50 nm, and the height of the
steep slope portion 322 relative to the flat portion 22 was set to
30 nm and the height of the slope portion 32 relative to the flat
portion 22 was set to 50 nm.
As a result, I.sub.leak/I.sub.oled was found to be 0.25, and the
amount of current upon application of a voltage of 1.5 V was found
below the limit of measurement (10.sup.-6 nA/pixel). As is clear
from the I.sub.leak/I.sub.oled of 0.25, the proportion of the
leakage current was high, and a very large leakage current flowed
between light emitting elements.
This has demonstrated the following: when the organic layer on such
a flat portion has an upper surface having a height larger than the
height of the upper end of the slope portion, crosstalk between
light emitting elements tends to be significant.
Comparative Example 3
An organic light emitting device was produced as in Example 1
except that the electron transport layer was formed so as to have a
layer thickness of 140 nm.
As a result, I.sub.leak/I.sub.oled was found to be 0.35, and the
amount of current upon application of a voltage of 1.5 V was found
below the limit of measurement (10.sup.-6 nA/pixel). As is clear
from the I.sub.leak/I.sub.oled of 0.35, the proportion of the
leakage current was high, and a very large leakage current flowed
between light emitting elements. This has demonstrated the
following: when the organic layer on the flat portion has an upper
surface having a height larger than the height of the upper end of
the slope portion, crosstalk between light emitting elements tends
to be significant.
Since the electron transport layer was formed with a layer
thickness of 140 nm, the resultant organic layer on the lower
electrode had a total thickness of 182 nm, which was larger than in
Example 1. As a result, the following Formula (5) was not
satisfied, so that the .lamda./4 interference condition was not
satisfied.
(.lamda./8).times.(-(2.PHI./.pi.)-1)<L<(.lamda./8).times.(-(2.PHI./-
.pi.)+1) (5)
As a result, the amount of current upon application of a voltage of
5 V was found to be 6 nA/pixel, and the luminance was found to be
90 cd/m.sup.2; thus, the amount of current and the luminance were
small. This was inferentially caused because the organic layer on
the lower electrode was formed with the increased thickness, which
resulted in an increase in the resistance.
Comparative Example 4
An organic light emitting device was produced as in Comparative
Example 1 except that, relative to the flat portion 21, the angle
of the steep slope portion 312 was set to 76.degree., and the angle
of the steep slope portion 322 was set to 76.degree.. Among the
layer thicknesses of the organic layer extending along the slope
portion 31 and the slope portion 32 measured in a direction
perpendicular to such a slope portion, the layer thickness of the
thinnest portion (hereafter, organic layer minimum thickness) was
found to be 19 nm. The amount of current upon application of a
voltage of 1.5 V was found to be 3.times.10.sup.-4 nA/pixel.
Example 2
An organic light emitting device was produced as in Example 1
except that, relative to the flat portion 21, the height of the
steep slope portion 312 was set to 70 nm, and the height of the
steep slope portion 322 was set to 70 nm. The organic layer minimum
thickness was found to be 20 nm. The amount of current upon
application of a voltage of 1.5 V was found to be 3.times.10.sup.-5
nA/pixel.
Example 3
An organic light emitting device was produced as in Example 1
except that, relative to the flat portion 21, the height of the
steep slope portion 312 was set to 65 nm, and the height of the
steep slope portion 322 was set to 65 nm. The organic layer minimum
thickness was found to be 25 nm. The amount of current upon
application of a voltage of 1.5 V was found to be 7.times.10.sup.-6
nA/pixel.
Example 4
An organic light emitting device was produced as in Example 1
except that, relative to the flat portion 21, the height of the
steep slope portion 312 was set to 58 nm, and the height of the
steep slope portion 322 was set to 58 nm. The organic layer minimum
thickness was found to be 29 nm. The amount of current upon
application of a voltage of 1.5 V was found to be 4.times.10.sup.-6
nA/pixel.
FIG. 13 illustrates the relation of the leakage current between the
upper electrode and the lower electrode against, among the layer
thicknesses of the organic layer on the slope portions measured in
a direction perpendicular to such a slope portion, the layer
thickness of the thinnest portion. Specifically, FIG. 13
illustrates, in organic light emitting devices of Comparative
Examples 1 and 4 and Examples 1, 2, 3, and 4, the relation of the
leakage current between the upper electrode and the lower electrode
against, among the layer thicknesses of the organic layer extending
along the slope portion 31 and the slope portion 32 measured in a
direction perpendicular to such a slope portion, the layer
thickness of the thinnest portion (organic layer minimum
thickness).
FIG. 13 has demonstrated the following. When the region of the
organic layer extending along the slope portions includes a portion
having a layer thickness of less than 20 nm, a large leakage
current flows between the upper electrode and the lower electrode.
By contrast, when the region of the organic layer extending along
the slope portions has a layer thickness of 20 nm or more, the
leakage current between the upper electrode and the lower electrode
is less than 1.times.10.sup.-4 nA/pixel, so that good
characteristics are maintained. When the region of the organic
layer extending along the slope portions has a layer thickness of
25 nm or more, the leakage current between the upper electrode and
the lower electrode is less than 1.times.10.sup.-5 nA/pixel, which
provides even better characteristics.
Comparative Example 4
An organic light emitting device was produced as in Example 1
except that the insulating layer was formed so as to have the
structure illustrated in FIG. 5A, the slope angle of the slope
portion 31 was set to 67.degree., and the slope angle of the slope
portion 32 was set to 40.degree.. The pixels each have a hexagonal
shape. Thus, the slope portion 31 is constituted by regions that
correspond to the sides of the hexagon, and that are numbered 1 to
6 counterclockwise from the side on the right in FIG. 2.
In the organic light emitting device of this Comparative Example, a
current of 1 nA/pixel was applied to 25 pixels. This resulted in
the occurrence of a phenomenon of a decrease in the emission
intensity at the inner periphery of each opening. This phenomenon
of a decrease in the emission intensity at the inner periphery of
the opening occurred differently depending on the sides of the
hexagon. This has been found to be associated with the layer
thickness of the region of the organic layer extending along the
slope portion. The results are described in Table 1.
Table 1 has demonstrated the following. When the layer thickness of
the region of the organic layer extending along the slope portion
is 33 nm or more, the phenomenon of a decrease in the emission
intensity at the inner periphery of the opening does not occur,
which means that a reduction is achieved in the leakage current
between the upper electrode and the lower electrode.
TABLE-US-00001 TABLE 1 Layer thickness of Percentage of occurrence
of Sides of organic layer on phenomenon of darkening in hexagon
slope portion peripheral region of opening No. 1 27 nm 48% No. 2 29
nm 44% No. 3 33 nm 0% No. 4 35 nm 0% No. 5 31 nm 36% No. 6 26 nm
52%
Advantageous Effects of Embodiments
Some embodiments of the present disclosure provide an electronic
device including a plurality of first electrodes that achieves a
reduction in the leakage current between the plurality of first
electrodes, and a reduction in the leakage current between such a
first electrode and the second electrode. While the present
disclosure has been described with reference to example
embodiments, it is to be understood that the disclosure is not
limited to the disclosed example embodiments. The scope of the
following claims is to be accorded the broadest interpretation so
as to encompass all such modifications and equivalent structures
and functions.
This application claims the benefit of Japanese Patent Application
No. 2019-023783, filed Feb. 13, 2019, and 2019-210033, filed Nov.
20, 2019, which are hereby incorporated by reference herein in
their entirety.
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